When, for example, the cardiac perfusion, i.e. the circulation of blood through the heart, in a patient is to be examined by means of a magnetic resonance tomography (MRT) system, the cardiac perfusion is typically measured in a rest state on the one hand and in a stress state on the other. This is necessary because it can only be ascertained when coronary vessels are dilated under stress whether a stenosis, in other words a narrowing of the vessels, is functionally relevant. In the rest state the stenosis is usually “masked” by the compensatory dilation of the vessel. This means that a blood flow typical of the rest state is ensured owing to the elasticity of the vessel in spite of the narrowing. Only under stress does the blood flow rate increase to such an extent that that the narrowing possibly can no longer be compensated for by the elasticity of the vessel. Accordingly it is only revealed in the stress state whether a further opening of the vessel is possible or whether the functioning of the vessel is compromised by the narrowing to a point where it becomes problematic.
When the patient is undergoing the MRT examination, the stress state for the heart can be induced only with extreme difficulty by means of a physical stressing of the patient. Moreover, some patients are in a condition which is not conducive to their being exposed to a physical stress. For this reason the stress state for the heart is often initiated by administering a chemical substance to the patient by means of an injection.
In such a scenario it is common practice at the present time to select a dose for the patient based on the patient's body weight from a table and to inject said dose during the actual examination. The examination of the patient by means of the imaging modality, in other words the MRT system, is accordingly carried out independently of how the patient actually responds to the injection, so that the desired specification of the stress state for the purpose of investigating the cardiac perfusion is only possible to a limited extent in this case. In principle no coordination takes place between the dosage, the injection and the actual examination.